You could say it’s a dead floss. After almost 40 years, the US Government has quietly dropped its recommendation that people should floss daily to prevent gum disease and cavities because there’s little proof it works.
Washington has recommended flossing since 1979, first in a surgeon-general’s report and later in the Dietary Guidelines for Americans, issued every five years. Under the law, those guidelines must be based on scientific evidence.
Last year the Associated Press asked the health and agriculture departments for their evidence. When the latest dietary guidelines appeared this year, the flossing recommendation had been removed.
The government acknowledged to AP the effectiveness of flossing had never been researched.
AP looked at the most rigorous research over the past decade, focusing on 25 studies that generally compared using a toothbrush with the combination of toothbrush and floss.
It found the evidence for flossing is “weak, very unreliable”, of “very low” quality, and carries “a moderate to large potential for bias”.
“The majority of available studies fail to demonstrate that flossing is generally effective in plaque removal,” said a 2015 review. A 2011 study credited floss with a slight reduction in gum inflammation, which can sometimes develop into gum disease. However, the reviewers ranked the evidence as “very unreliable” and a dental magazine said any benefit would be so small that users might not notice.
The American Dental Association and American Academy of Periodontology (specialists in gum disease and implants) cited other studies as proof of their claims that flossing prevents buildup of gunk known as plaque, early gum inflammation called gingivitis, and tooth decay.
However, most of these studies used outdated methods or tested few people. Some lasted only two weeks, far too short for a cavity or dental disease to develop. One tested 25 people after a single use of floss.
Periodontists’ president Wayne Aldredge acknowledged the weak scientific evidence. Still, he urges his patients to floss. “It’s like building a house and not painting two sides of it,” he said. “Ultimately, those two sides are going to rot away quicker.”
Aldredge also said many people use floss incorrectly, moving it in a sawing motion instead of up and down the sides of the teeth.
Global giants Procter & Gamble and Johnson & Johnson “own” the flossing business, predicted to reach almost $US2 billion next year. The industry has paid for most studies and sometimes designed and conducted the research.
US dentist Levi Spear Parmly is credited with inventing floss in the early 19th century. The ADA has been promoting it since 1908.
On the downside medical literature suggests careless flossing can damage gums, teeth and dental work. It can also dislodge bad bacteria that invade the bloodstream and cause dangerous infections, especially in people with weak immunity.